For a microwave transmission system, link availability is an important indicator for measuring link quality. The availability refers to a ratio of remaining available time except unavailable time to total working time of a device. In practical application, the link availability may be affected by factors such as weather variations and external signal interference.
QAM (Quadrature Amplitude Modulation, quadrature amplitude modulation) is a modulation scheme used by current mainstream microwave devices. Usually, the number of signal vector endpoints in a signal vector endpoint distribution map is used to define different modulation modes, for example, 16 QAM, 32 QAM, and 64 QAM. The larger the number, the higher the sensitivity will be, the larger a link transmission capacity will be, and the lower an anti-interference capability will be. For example, in a same channel bandwidth, in contrast to the 32 QAM modulation mode, the 64 QAM modulation mode has a higher sensitivity, a larger link transmission capacity, and a lower anti-interference capacity. For ease of description, in the specification, the modulation mode with a large number of signal vector endpoints is referred to as a high modulation mode and otherwise referred to as a low modulation mode.
In the current microwave system, ACM (Adaptive Coding and Modulation, adaptive coding and modulation mode) is a common method for improving the link availability. When microwave link signal quality deteriorates, the ACM function lowers the sensitivity of the microwave system by lowering a transmission modulation mode, to improve the link availability. When the microwave link signal quality recovers, the ACM function upgrades the transmission modulation mode again to increase the link transmission capacity.
In the prior art, in addition to the ACM, there are no other effective methods for improving the link availability. Further, the ACM technology cannot effectively improve the link availability in the situation where the modulation mode is already the lowest modulation mode, so that transmission of a high-priority service cannot be ensured.